a nmo Mineral Species. 113 



hydrochloric acid in the ordinaiy way for the separation of siUcic 

 acid : the alumina^ Hme and magnesia were determined as usual. 

 The silicic acid was attacked by hydrofluoric acid and found to 

 be piire. Oxygen. • 



Silicic acid . . . 50-70 26-86 6 



Alumina .... 1*48 



Lime 33-24 9-49 2 



Magnesia . . . 0-18 



Water .... 1418 1260 3 

 99-78 

 If we neglect the small quantity of alumina and magnesia as 

 non-essential elements, we find the oxygen in the other three 

 constituents to be nearly in the proportions of 6, 2 and 3, and 

 the mineral is consequently a hydrated silicate of lime represented 

 by the formula ^^^.^^^ g^Q3) + 3HO. 



The analysis shows a slight excess in the amount of lime, and 

 deficiency in the silicic acid and water required for the formula ; 

 but the latter is probably due to partial efflorescence, as I have 

 found that gm-olite loses water with great facility. 11-201 grs. 

 of it, dried in the water-bath, lost 0-495 gr., equal to 4-42 per 

 cent. This corresponds to one equivalent of water, the calcula- 

 tion of which gives 5-1 per cent. ; so that gurolite dried at 212° 

 is represented by the formula 2 (CaO, SiO^) + 2H0,or more simply 

 still, as a neutral silicate of lime with one equivalent of water. 



In its chemical constitution this new mineral stands in a very 

 simple relation to the other silicates of lime, of which three are 

 already known, one hydrated and two anhydrous. Their formulse 

 are — 



WoUastonite (tabular spar) . 3CaO, 2SiO'^ 

 " Kalk-trisilicat " of Gjelleback CaO, SiO\ 



Gurolite 2(CaO,Si03)-h3HO. 



Dysclasite (Okenite) . . . 3CaO, 4SiOH6HO. 

 In gurolite, then, we have the same compound of silicic acid 

 and lime as that existing in the Gjelleback mineral ; in the latter, 

 however, it is anhydrous, while in the former two equivalents of 

 the silicate are in combination with three of water. Its relation 

 to dysclasite is closer still ; in fact, by doubling its formula, the 

 difference is found to consist only in a single equivalent of lime. 

 To the latter mineral gurolite approximates also in some of its 

 physical characters, possessing the same toughness and difficulty 

 of pulverization, although in a very inferior degree. Its crystal- 

 lizaticm in plates and not in needles, its high lustre, and the ease 

 with which it loses water, distinguish it completely from dyscla- 

 site, and lender it an exceedingly distinct, well-marked, and cha- 

 racteristic species. 



Phi/. May. S. 4. Vol. 1 . No. 2. Feb. 1851. I 



